1. Field of Invention
This invention relates to a process for transferring a magnetic layer or a magnetic strip onto a permanent support.
2. Discussion of the Prior Art
The use of magnetic layers or magnetic strips for storing and recording information and other data has become widespread on a large variety of documents. Particular examples of this type of document include transportation tickets, highway toll tickets, credit cards, accounting cards, magnetic labels, etc. Magnetic strips (tracks) are also commonly used for providing the sound track on sound movie film.
Conventionally, the magnetic strip was permanently deposited on a substrate by a printing method using an ink containing a magnetic pigment. This technique proved to be unsuitable for obtaining a magnetic strip with good mechanical qualities such as flatness. The printing technique did not allow for obtaining magnetic recording of sufficient density to prevent the loss of information. Additionally, the printed magnetic strips were rough and caused premature wear of the reading heads.
One proposal to overcome these drawbacks was to directly fix a magnetic strip on the back of the support, for example, credit cards or similar tickets. In actual use, however, this process has the drawback of being expensive. In addition, the relatively large thickness of the magnetic strip prevented easy storage by superposition of a plurality of the cards or tickets. It therefore became necessary to provide a special housing to store the tickets and accordingly, increase the costs.
It has also been proposed, for example, in French Patent No. 1,250,712 and in U.S. Pat. Nos. 2,628,929, 2,909,442 and 3,497,411 to first form an intermediate magnetic strip on a temporary support and to transfer the magnetic strip to the permanent support while the magnetic coating is hot and under pressure. These processes have not, however, been entirely satisfactory since the application of heat tends to cause deformation of the permanent support or the magnetic strip resulting in irregularities of the magnetic properties of the transferred strip whose magnetic qualities are altered by the transfer. When the amount of heat transmitted to the magnetic strip is limited to avoid the occurrence of deformations, the rate of transfer becomes limited.
Also, the indirect transfer method of these patents generally requires the use of a separate adhesive layer to adhere the magnetic strip to the permanent support. This causes the thickness of the strip to be increased and also creates the possibility of additional irregularities in the qualities of the transferred magnetic strip.